Cognitive and social explanations of science should be complementary rather than competing. Mind, society, and nature interact in complex ways to produce the growth of scientific knowledge. The recent development and wide acceptance of the theory that ulcers are caused by bacteria illustrates the interaction of psychological, sociological, and natural factors. Mind-nature interactions are evident in the use of instruments and experiments. Mind-society interactions are evident in collaborative research and the flow of information among researchers. Finally, nature-society interactions are evident in the role of granting agencies in determining the availability of instruments and the funding of experiments.